Aqueous sulfo modified melamine-form-aldehyde resin composition containing multivalent oxides

ABSTRACT

AN AQUEOUS SOLUTION OF A MELAMINE-FORMALDEHYDE RESIN CONTAINING ENOUGH SULFO GROUPS TO BE WATER SOLUBLE COMBINED WITH ONE OR MORE BASIC OR AMPHOTERIC OXIDES OR HYDROXIDES OF TRIVALENT OR QUADRIVALENT METALS IS A STRONG BINDER FOR SAND, CEMENT, AND THE LIKE.

States Patent gm. or. C08g 9/30, 51/04 us. or. est-mat n x iismix c'r or. DlSCLOSURE 1.1: Anaqueous. solution of a melaminc-formaldehyde resin containing enough sulfo groups to be water soluble combined with one or more basic or amphoteric oxides or hydroxides of trivalent or quadrivalent metals is a strong 'flmagrter sand; cement, and the like.

"' Tliis 'invention relates to binders, and particularly to binders having a synthetic polymer component and an inor nic oxidecom'ponent.

:1 its more specific aspects, the invention is concerned withbinders" of the general type described in which the polymer component isainelamine-fori-naldehyde resin modified by means of sulfites or sulfonates to contain sulfo groups in anamount suflici'entto make the modified i'esitl-watersoluble. i i modified, watefisoluble melamine-formaldehyde "tesins have been' proposed' heretofore as binders for cementitious materials such as lime, cement, or plaster. It new been-found that the resins produce greatly im- 'pi ov'eil bends when used 'in conjunction with basic or amphoteric oxides and hydroxides of trivalent or quadrivalent metals.

Typical oxides which may be used in the binders of the'irrventiorrin the anhydrous or hydrated condition, that is; as hydroxides, include A1 0 TiO,, Fe O Cr 0 P939, and the oxides-0f the rare earth metals. They may .bei'present in the binderspartly in the form of cements, ignch as portlandcement or high alumina cement, 97.5% .exide or hydroxide in the form of cement being the *hormal limit at which significant beneficial results can The found The ratio'resin to oxide or hydroxide may vary within wide limits, best results usually being achieved at ratios between 1:25 and 2:1.

The binders of the invention have been used successfully in the preparation of shaped bodies from granular material, such-as foundry cores and linings for permanent foundry molds:- The binder is intimately mixed with the granular filler, and the mixture so obtained is shaped under pressure and dried. "Good results have also been achieved with the binders of the'invention in adhesively connecting structural elements such as bodies of aerated concrete. When the oxides employe'd are colored, as the chromium and iron oxides are, pigmented cementitious bodies of great mechanical strength are readily produced.

The resins employed in the binders of the invention are prepared in a known manner from melamine and form- Patented May 9, 1972 aldehyde, and modified by reaction with sulfonating agents, such as sodium metabisulfite or suliamic acid to produce -SO H groups, one SO H group per melamine radical being normally sufficient to produce the desired solubility in water. The condensation reaction between the melamine and the formaldehyde is carried out until the mixture reaches a desired viscosity, generally between 10 and 150 centipoise at 20 C., and the condensation product is then sulfonated to produce CH SO H or CH,--NH-SO H groups. As a general rule, resins having a high viscosity are employed most successfully with relatively large amounts of free oxides or hydroxides and small amounts of cement, whereas resins of lower viscosity are best suited for binders containing a relatively small amount of free oxides or hydroxides and much cement.

The following examples are further illustrative of the invention, and it will be understood that the invention is not limited thereto. All parts and percentages are by weight unless stated otherwise.

EXAMPLE I 567 parts 37% formaldehyde solution were adjusted to pH 4.5 with sodium hydroxide, and 294 parts melamine were added. The mixture was heated to 80 C. until a clear solution was formed. The solution was cooled to 45 C., and 222 parts sodium metabisulfite, Na S O were added and followed by 332 parts water and enough sodium hydroxide to adjust the pH to 10.5. The solution so obtained was heated to 80 C. for two hours, and cooled to 50 C. 750 parts concentrated sulfuric acid diluted with 2116 parts water were added, and the resulting mixture was kept for ten hours at 50 C., whereupon it was adjusted to pH 9.5 with sodium hydroxide.

The liquid obtained was miscible with water in all proportions. It contained 20% solids and had a viscosity of 81 centipoise as determined with a Brookfield viscosimeter at 20 rpm. at 20 C.

EXAMPLE 2 A mixture of 400 parts aqueous 30% formaldehyde solution having a pH of 8.2 was stirred with 126 parts melamine and heated to 80 C. until a clear solution was obtained. The solution was heated to its boiling point, there was added a solution of 97 parts sulfamic acid in enough dilute sodium hydroxide solution to make the pH 7.2, and heating was continued for five minutes. The mixture was then cooled while 500 parts water were admixed.

The solution so obtained was miscible with water in all proportions, contained about 27% solids, and had a viscosity of 14 centipoise determined as in Example 1.

EXAMPLE 3 567 parts 37% aqueous formaldehyde were adjusted with sodium hydroxide to pH 4.0, and 294 parts melamine were added. The mixture was heated to C. to produce a clear solution which was cooled to 45 C. 222 parts sodium metabisulfite were added, and thereafter 332 parts water, whereupon the reaction mixture was adjusted to pH 10.5, and heated to C. for two hours. After cooling to 50 C., 70 parts concentrated sulfuric acid diluted with 2116 parts water were added, and the resulting mixture was heated to 50 C. for four hours, and then adjusted to pH 9.0 with sodium hydroxide.

:4 the binder compositions listed in Table 2, and a second plate of the same dry aerated concrete was 'held against each coated surface with light pressure for about 20 hours. The bonded structures so obtained were tested to destruc- The liquid so obtained was miscible with water in all tion. At least 30% of the fracture in each case occurred proportions, had a solids content of 20%, and a viscosity of within one of the concrete pieces, not in the bond.

13 centipoise at 20 C. as determined with the afore-men- All but two binder compositions contained 50 parts tioned 'viscosimeter. portland cement (P) or high alumina cement (Q), the inv M PL 4 dicated amount of resin solution, as prepared in Example 1 or 2 and contributing up to 40% water, and an Specimens of shell mold linings were prepar from oxide or hydroxide identified partly by capital letters as silica sand, saw dust, inorganic oxides or hydroxides, and in Table 1 with the f ll i addition:

the synthetic resin solution prepared in Example 1 and are listed in Table 1. One set of each composition was dried (G) Rad F 514% P6203 155% f g T102 for 5-10 hours at 80 c. and 24 hours at 120 c. An- 71% S102 C30, 109% 011 other set was stored for one week at about C. Speci- TABLE .2

mens from each set were subjected to the bending test of 1; v a ,r

the German Industrial Standard DIN 1164. Table 1 lists Cement hydroxide Partfsolutlbn V the results of the bending tests in kgJcmF. None A W The added oxides or hydroxides are identified in Table 1 20 D G by capital letters as follows: 1 g i g (A) Aluminum hydroxide containing 99%+ Al(OH) (B) Greek bauxite: 52.0% A1 0 22.5% Fe,o,, 5.3% Q: G ;....d0..t..-.. 50 $0,, 15.5%losson ignition. 25 g v 23 (C) Surinam bauxite: 60.3% A1 0 1.8% F6 0;, 46 Q: -I B 40 SiO 31.5% loss on ignition. r

(D) Calcined bastnesite: 90.2% rare earth oxides (about Control specimenstprepared in an otherwise identical 25% Lagog, 40% CeO 20% P130, and Nd O 5% manner without the resin did not show appreciablebond Sm=0 balance oxides of Y and Th), 3.9% F, 0.7% strength. ,j loss on ignition. EXAMPLEfi A,

(E) Titania: at least 99% TiO,. 5 r i pecunens were prepared fromwhite portland cement g i i ggfig ggz F6303 13% and various amounts of water, chromium sesquioxide, and of the resin solution prepared in Example 3. The proce- TABLE 1 dure followed was generally that of German Industrial Standard DIN 1164. The specimens had dimensionsnf R 1 Binding i i 4 x 4 x 16 cm and a slump test value of 18+! cm They $52 55 Pam solutiagnli i g were packed tight in respective molds on a? shock table pans according to the proposed international standard RILEM- 38 $8 40 CEM, unmolded after one day, and stored in a controlled B 150 150 14 18 atmosphere at 20 C. at 65% relative humidity. 1 g 538 :33 1'} Table 3 lists the additions of resin solution; ofchromig 300 400 13 16 um sesquioxide and of water used in percent based on the 83 4 3 g weight of the portland cement, and the results of bending E 100 200 11 7 tests and of compression tests in lap/cm as determined $3 3 after 1,7, and 28 days. ?Jw' E 200 400 11 15 The superior elfects achievedby the simultaneous addition of the chromium sesquioxide and ofthe .resin'are evident. z TABLE 3 v I y Rf t? C 0 w t Bending stgggfh, kpJem. Compress. gtttrgrn tnknlemd 80 11 on I 8 l percent pertierit pereeh t ldny 7days fl'dey's ,1 days. Idays Ztldnys 0 a4 51 62 195 rm 420 o 42 74 82 380 51a aa9 0 41 51 7s 76 350 573 554 2.5 52 32 50 61 m0 403 454 2.5 43 54 84 a4 ass s39 664 2.5 40 as 83 104 355 e42 699 i1" rt When specimens from the several sets were tested in What is claimed is: r a

an iron foundry in actual use, they were found satisfac- 1. .A binder composition consisting essentially'of tory in their properties when in contact with the molten (a) a melamine formaldehyde resin modified to conmetal. They did not produce a strong unpleasant odor, tain one sulfo group per melamine radicaland wate'r and no hydrogen cyanide could be detected. They did not soluble;

lose weight to a significant extent by melting, and they (b) a basic or amphoteric oxide of at least one-tridid not or did not significantly react with the molten valent or quadrivalent metalselected from thegroup metal, as would be indicated by gas development and ns i g f aluminum, titanium,

boiling ofthe m lt, lead, and the rare earth metals;'-'and (c) an amount of water up to 40% and sufiicient'to EXAMPLE 5 dissolve said resin, Plates of dry, aerated concrete having a compressive the ratio of said resin to'said oxide beingbetween strength of 25 kp./cm. were coated with thin layers of 1:25 and 2:1. t

2. A composition as set forth in claim 1, wherein up 3,465,824 9/1969 Kucera 106- -90 X to 97.5% of said oxide is a constituent of portland 08- 2,407,599 9/1946 Auten et a]. 26029.4 UX ment and is present in said composition in the form of 2,840,483 6/1958 Morgan et al. 106-90 X said portland cement. 2,798,003 7/ 1957 Morgan et a1. 106-90 References Cited DONALD J. ARNOLD, Primary Examiner UNITED STATES PAT J. B. LOWE, Assistant Examiner 2,539,446 1/1951 Lies 260-39 M UK US. CL

2,863,842 12/1958 Bonzagni 260-67.6 X

2,711,219 6/1955 Salathiel 106-90 UX M39? 3,216,966 11/1965 Collins 106--9OX 

